It is well known that in motor/fan assemblies, a motor/fan shaft is typically maintained within a bearing received within a bore in the fan end bracket. In the past, such fan end brackets have typically been of metal construction, formed by a stamping or metal die casting process. Similarly, the cup adapted for receiving the bearing has typically been pressed or stamped into a support member that traverses an end of the fan end bracket. Bearing-receiving cups or receptacles have typically been accurately formed by the press or stamping process. Accordingly, the bearing can be easily placed into its receptacle during the manufacturing and motor assembly process.
Recently, it has become desirable to form many of the structural components of motors from molded plastics. It has particularly become known to employ thermoset plastics for that purposes. However, shrinkage and the like which is experienced when a molded piece cools or is cured often results in distortion of various features on the molded part. Specifically, when using fiberglass reinforced thermoset polyester, it has been found that the bearing cup at the end of the fan end bracket is given to distortion during the cooling/curing process of the thermoset material unless great care is given in the manufacturing process. When the bore is made as a complete cylindrical bore, defined by a cylindrical wall, the bore often deforms to an elliptical or egg shape in cross section, rather than a circular configuration as is necessary for receiving the bearing. As a consequence, there is a high rejection rate of such molded fan end brackets, while even those which might be acceptable require significant reworking. Simply stated, the rejection rate or the rework rate of such molded fan end brackets has been found to be undesirably high. Moreover, with the wall of the bearing bore being designed to make total circumferential contact with the bearing, the necessary rework to attain that constant receipt is significant.
While the molding of fan end brackets and other motor/fan assembly parts from thermoset materials is highly desirable, the rejection or rework rate for such parts often negates the benefits achieved over the prior art metal stamped or die castparts. Notably, the primary area of concern with respect to the fan end bracket is that the bearing bore be sufficiently configured to nestingly receive the bearing during the manufacturing process. The other problems inherent with the plastic molding process have been less egregious.
In view of the foregoing, it is most desirable that a molded thermoplastic fan end bracket be devised that has either a uniformly formed bearing receptacle, or one which has minimal distortions which are easily reworked.